Adjustable height PIF probe

ABSTRACT

A plasma probe assembly for use in a plasma processing chamber is provided. A semiconductor probe element with a probe surface at a first end of the semiconductor probe element is provided. An electrical connector is electrically connected to the semiconductor probe element. An electrically insulating sleeve surrounds at least part of the probe element. An adjustment device is connected to the semiconductor probe so that the probe surface is coplanar with an interior chamber surface of the plasma processing chamber.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of prior U.S. patent application Ser.No. 11/377,074, entitled “Adjustable Height PIF Probe”, filed on Mar.15, 2006, by inventors Kimball et al., which is incorporated herein byreference and from which priority under 35 U.S.C. §120 is claimed.

BACKGROUND OF THE INVENTION

The present invention relates in general to substrate manufacturingtechnologies and in particular to an apparatus for measuring a set ofelectrical characteristics in a plasma.

In the processing of a substrate, e.g., a semiconductor wafer, MEMSdevice, or a glass panel such as one used in flat panel displaymanufacturing, plasma is often employed. As part of the processing of asubstrate (chemical vapor deposition, plasma enhanced chemical vapordeposition, physical vapor deposition, etch, etc.) for example, thesubstrate is divided into a plurality of dies, or rectangular areas,each of which will become an integrated circuit. The substrate is thenprocessed in a series of steps in which materials are selectivelyremoved (etching) and deposited (deposition) in order to form electricalcomponents thereon.

In an exemplary plasma process, a substrate is coated with a thin filmof hardened emulsion (such as a photoresist mask) prior to etching.Areas of the hardened emulsion are then selectively removed, causingparts of the underlying layer to become exposed. The substrate is thenplaced in a plasma processing chamber on a substrate support structurecomprising a mono-polar or bi-polar electrode, called a chuck.Appropriate etchant source gases (e.g., C4F8, C4F6, CHF3, CH2F3, CF4,CH3F, C2F4, N2, O2, Ar, Xe, He, H2, NH3, SF6, BC13, C12, etc.) are thenflowed into the chamber and struck to form a plasma to etch exposedareas of the substrate.

Subsequently, it is often beneficial to measure the electricalcharacteristics in a plasma (i.e., ion saturation current, electrontemperature, floating potential, etc.) in order to ensure consistentplasma processing results. Examples may include detecting the endpointof a chamber conditioning process, chamber matching (e.g., looking fordifferences between chambers which should nominally be identical),detecting faults and problems in the chamber, etc.

In view of the foregoing, there are desired apparatus for measuring aset of electrical characteristics in a plasma.

SUMMARY OF THE INVENTION

To achieve the foregoing and in accordance with the purpose of thepresent invention, a plasma probe assembly for use in a plasmaprocessing chamber is provided. A semiconductor probe element with aprobe surface at a first end of the semiconductor probe element isprovided. An electrical connector is electrically connected to thesemiconductor probe element. An electrically insulating sleeve surroundsat least part of the probe element. An adjustment device is connected tothe semiconductor probe so that the probe surface is coplanar with aninterior chamber surface of the plasma processing chamber.

In another manifestation of the invention, a plasma probe assembly foruse in a plasma processing chamber is provided. A semiconductor probeelement with a semiconductor probe surface at a first end of thesemiconductor probe element is provided. An electrical connector iselectrically connected to a second end of the semiconductor probeelement. An electrically insulating sleeve surrounds at least part ofthe probe element. An adjustment device is connected to thesemiconductor probe element to adjust the semiconductor probe element sothat the probe surface is coplanar with an interior chamber surface ofthe plasma processing chamber. A sleeve adjustment device adjusts theelectrical insulating sleeve, wherein the electrically insulating sleevehas an external edge and the sleeve adjustment device adjusts theexternal edge to be coplanar to the probe surface. Sensing electronicsis electrically connected to the electrical connector, wherein thesensing electronics comprises an ammeter.

These and other features of the present invention will be described inmore detail below in the detailed description of the invention and inconjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 is a schematic view of a process chamber that uses a plasmaprobe.

FIG. 2 is a schematic view of another process chamber that uses a plasmaprobe.

FIG. 3 is a perspective view of a plasma probe.

FIG. 4 is a cross-sectional of the plasma probe of FIG. 3 along cutlines A-A.

FIG. 5 is an enlarged cross-sectional view of a chamber wall and aprobe.

FIG. 6 is a cross-sectional view of another plasma probe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference toa few preferred embodiments thereof as illustrated in the accompanyingdrawings. In the following description, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one skilled in the art, thatthe present invention may be practiced without some or all of thesespecific details. In other instances, well known process steps and/orstructures have not been described in detail in order to notunnecessarily obscure the present invention.

FIG. 1 is a simplified diagram of an inductively coupled plasmaprocessing system in which the inventive plasma ion flux (PIF) probe 140is used. Generally, an appropriate set of gases may be flowed from gasdistribution system 122 into plasma chamber 102 having plasma chamberwalls 117. These plasma processing gases may be subsequently ionized ator in a region near injector 109 to form a plasma 110 in order toprocess (e.g., etch or deposit) exposed areas of substrate 114, such asa semiconductor substrate or a glass pane, positioned with edge ring 115on an electrostatic chuck 116.

A first RF generator 134 generates the plasma as well as controls theplasma density through an upper electrode 104, while a second RFgenerator 138 generates bias RF, commonly used to control the DC biasand the ion bombardment energy. Further coupled to source RF generator134 is matching network 136 a, and to bias RF generator 138 is matchingnetwork 136 b, that attempt to match the impedances of the RF powersources to that of plasma 110. Furthermore, vacuum system 113, includinga valve 112 and a set of pumps 111, is commonly used to evacuate theambient atmosphere from plasma chamber 102 in order to achieve therequired pressure to sustain plasma 110 and/or to remove processbyproducts.

The PIF probe 140 is mounted so that a surface of a probe element iscoplanar with the interior of the chamber walls 117. Sensing electronics142 are electrically connected to the PIF probe 140.

FIG. 2 is a simplified diagram of a capacitively coupled plasmaprocessing system in which the inventive plasma ion flux (PIF) probe 240is used. Generally, capacitively coupled plasma processing systems maybe configured with a single or with multiple separate RF power sources.Source RF, generated by source RF generator 234, is commonly used togenerate the plasma as well as control the plasma density viacapacitively coupling. Bias RF, generated by bias RF generator 238, iscommonly used to control the DC bias and the ion bombardment energy.Further coupled to source RF generator 234 and bias RF generator 238 ismatching network 236, which attempts to match the impedance of the RFpower sources to that of plasma 220. Other forms of capacitive reactorshave the RF power sources and match networks connected to a topelectrode 209. In addition, there are multi-anode systems such as atriode that also follow similar RF and electrode arrangements.

Generally, an appropriate set of gases is flowed through an inlet in thetop electrode 209 from gas distribution system 222 into plasma chamber202 having plasma chamber walls 217. These plasma processing gases maybe subsequently ionized to form a plasma 220, in order to process (e.g.,etch or deposit) exposed areas of substrate 214, such as a semiconductorsubstrate or a glass pane, positioned with edge ring 215 on anelectrostatic chuck 216, which also serves as an electrode. Furthermore,vacuum system 213, including a valve 212 and a set of pumps 211, iscommonly used to evacuate the ambient atmosphere from plasma chamber 202in order to achieve the required pressure to sustain plasma 220.

FIG. 3 is a perspective view of a PIF probe 140 provided by anembodiment of the invention. FIG. 4 is a cross sectional view of the PIFprobe 140 of FIG. 3 along cut lines A-A. A silicon probe element 304provides a probe surface 308 at a first end of the probe element, whichis a surface used for plasma detection. An aluminum electrical connector312 is placed at a second end of the probe element away from the probesurface 308. An electrically insulative sleeve 316 is placed around thefirst end of the probe element 304. A segmented cover 320 is placedaround the second end of the probe element 304 and the electricalconnector 312. In this embodiment, the segmented cover 320 has a firsthalf 320 a and a second half 320 b that are held together by an O-ring324.

The probe element 304 has a wide first end to provide a wide probesurface 308. A narrower neck 310 connects the first end of the probeelement 304 to the second end 314 of the probe element 304. In thisembodiment, the back surface of the second end 314 of the probe element304 is metalized to provide a good electrical contact between the probeelement 304 and the aluminum electrical connector 312.

Each of the segment cover halves 320 a,b have a first lip 332 forengaging with the second end 314 of the probe element and a second lip336 for engaging with the electrical connector 312. In this embodiment,the second lip 336 has a beveled surface that engages with theelectrical connector 312 at an oblique angle to form an obliqueconnection, as shown, so that the electrical connector 312 is pressedagainst the metalized surface of the second end 314 of the probe element304 as the O-ring 324 presses the segmented cover halves 320 a,btogether to provide a good electrical contact. In other embodiments, theelectrical connector 312 has a beveled surface to create the obliqueconnection between the second lip and the electrical connector. In otherembodiments, the second end 314 of the probe element has an obliqueconnection with a lip of the segmented cover.

A shaft 352 is connected to the electrical connector 312. The shaft 352may screw into the electrical connector 312.

The probe element 304 in this embodiment is made of silicon forcontamination purposes. Preferably, the probe element is of a materialthat would be available from other sources during the etch. In addition,it is preferable that the probe element is made of a semiconductormaterial. In this embodiment, the sleeve 316 is made of quartz. Thecover 320 is made over a fluoropolymer.

In assembling the probe 140, at least one spacer 340 is placed aroundthe neck 310 of the probe element 304. The second end 314 of the probeelement passes through an aperture with the sleeve 316. A lip 338 formedby the sleeve engages with the spacer 340. The spacers 340 are added orremoved until an external edge of the sleeve 316 is about even with theprobe surface 308, when the lip is against the spacers 340. It isbelieved that the quartz sleeve will erode faster than the silicon probeelement 304, so initially spacers are desired, so as the sleeve 316erodes faster spacers may be removed to keep the probe surface abouteven with the external edge of the sleeve 316.

The electrical connector 312 is placed against the second end 314 of theprobe element 304. The segmented cover 320 is placed around the secondend 314 of the probe element 304 and the electrical connector 312.O-ring 324 is placed around the segmented cover 320, compressing thesegmented cover 320 together, which pushes the electrical connector 312against the metalized surface of the second end 314 of the probe element304 to provide a good electrical contact, thus forming the probe 140.The probe 240 may be placed from the inside of the chamber into a probeaperture into which the shaft 352 extends. The shaft 352 may be insertedinto a hole in the electrical connector 312, where the shaft 352 and thehole have matching threads. The shaft 352 provides both an electricalcontact and mechanical support for the probe 140.

The shaft 352 allows for easy mounting of the probe 140. The shaft 352may be adjusted or allows adjustment of the probe so that the probesurface 308 and the external edge of the sleeve 316 are substantiallycoplanar with the chamber surface.

Preferably, the probe surface 308 and the external edge of the sleeve316 are coplanar to the surface of the chamber. The quartz external edgeof the sleeve 316, the probe surface 308, and the upper electrode 104,may be made of different materials, and therefore may wear out or erodeat different rates, causing the probe surface 308 or the external edgeof the sleeve 316 to not be coplanar with the surface of the chamber.

FIG. 5 is an enlarged cross-sectional view of a chamber wall 117 and aprobe 140. The shaft 352 extends from the probe 140 and is connected toa first end of a shaft holder 360. A second end of the shaft holder isconnected to a first end of an electrical vacuum feed through 364. Thegrounded part of the feed through 366 is secured the backside of thechamber wall 117. A spring 368 between the feed through 364 and theshaft holder 360 maintains the force required for good thermal contactbetween the chamber wall 117 and the shaft holder 360. The shaft holder360 is electrically insulated from the chamber wall 117 by anelectrically insulating and thermally conducting material 362. Suchmaterials include, but are not limited to, aluminum nitride, aluminumoxide, silicon nitride, boron nitride, and polymers filled with theseceramics.

In operation, a screwdriver, wrench, or other drive device may be usedto rotate the shaft holder 360 which is threaded onto the probe shaft352. This operation is done with the electrical feed through 364removed. Depending on the rotation of the shaft holder 360, the probeshaft 352 and probe 140 are slid either towards or away from the shaftholder 360 and the back side of the chamber wall 117, allowing the probesurface 308 to be adjusted with respect to the inner surface of thechamber wall 117.

The ability to adjust the probe and sleeve independently allows theprobe to be mounted inside the chamber for easier adjustability. If thequartz sleeve 316 is eroded faster than the probe element 304, aftersignificant erosion of the quartz sleeve 316, a spacer 340 may beremoved so that the external edge of the quartz sleeve 316 is aboutcoplanar with the probe surface 308.

In operation, the probe 140 measures the plasma by measuring the currentat the probe surface. The current may flow from the probe surfacethrough the probe element to the electrical connector and then to thesupport shaft to the sensing electronics. Therefore, the sensingelectronics comprises a device for measuring and recording current, suchas an ammeter. The plasma causes etching of the external edge of thesleeve and the probe surface of the probe element. If the external edgeis etched faster, so that the external edge is etched further than theprobe surface, the probe is removed and then a spacer is removed fromthe probe until the external edge is about coplanar with the probesurface. The etching may then be continued.

Other probe adjustment mechanisms may be used in other embodiments toadjust the surface of the probe to be coplanar to the chamber surface,such as allowing the probe to be screwed further onto the shaft. Suchprobe adjustment mechanisms are preferably connected to the shaft, butmay be performed through other devices. The spacers allow the externaledge of the sleeve to be kept coplanar with the surface of the probe asthe external edge of the sleeve and the surface of the probe erode atdifferent speeds. Other sleeve adjustment mechanisms may be used inother embodiments to adjust the external edge of the sleeve to be keptcoplanar with the surface of the probe. Such sleeve adjustmentmechanisms are preferably disposed between the probe and the sleeve.

FIG. 6 is a cross-sectional view of a probe 640 provided by anotherembodiment of the invention. The probe 640 comprises a probe element 604with a probe surface 608. A wire mesh spring and an elastomer adhesivebond 620 electrically and mechanically connect a second end of the probeelement 604 to an electrical connector 612. A support shaft 652 isconnected to the electrical connector 612. An electrically insulativesleeve 616 surrounds the probe element 604 and the electrical connector612. In an alternative embodiment, probe element 604 can be bonded toelectrical connector 612 by brazing.

While this invention has been described in terms of several preferredembodiments, there are alterations, permutations, and various substituteequivalents, which fall within the scope of this invention. It shouldalso be noted that there are many alternative ways of implementing themethods and apparatuses of the present invention. It is thereforeintended that the following appended claims be interpreted as includingall such alterations, permutations, and various substitute equivalentsas fall within the true spirit and scope of the present invention.

1. A plasma processing chamber, comprising: a chamber wall forming aplasma processing chamber enclosure; a substrate support for supportinga wafer within the plasma processing chamber enclosure; at least oneelectrode for providing power to the plasma processing chamber enclosurefor sustaining a plasma; a gas inlet for providing gas into the plasmaprocessing chamber enclosure; a gas outlet for exhausting gas from theplasma processing chamber enclosure; and a plasma probe assembly formeasuring electrical characteristics of the plasma, comprising: a probeelement with a probe surface at a first end of the probe element; anelectrical connector electrically connected to the probe element; anelectrically insulating sleeve surrounding at least part of the probeelement; and an adjustment device connected to the probe element toadjust the probe element so that the probe surface is coplanar with aninterior surface of the chamber wall.
 2. The plasma processing chamber,as recited in claim 1, wherein the plasma probe assembly furthercomprises a wire mesh spring and elastomer adhesive electricallyconnecting the second end of the probe element to the electricalconnector.
 3. The plasma processing chamber, as recited in claim 1,wherein the plasma probe assembly further comprises a wire brazed to theprobe element and brazed to the electrical connector.
 4. The plasmaprocessing chamber, as recited in claim 1, wherein the plasma probeassembly further comprises: a segmented cover surrounding the electricalconnector and at least part of the probe element; and at least oneO-ring surrounding the segmented cover.
 5. The plasma processingchamber, as recited in claim 1, wherein the probe surface is silicon. 6.The plasma processing chamber, as recited in claim 1, wherein the plasmaprobe assembly further comprises sensing electronics electricallyconnected to the electrical connector, wherein the sensing electronicscomprises an ammeter.
 7. The plasma processing chamber, as recited inclaim 1, wherein the electrically insulating sleeve is quartz.
 8. Theplasma processing chamber, as recited in claim 1, wherein the plasmaprobe assembly further comprises a sleeve adjustment device foradjusting the electrical insulating sleeve, wherein the electricallyinsulating sleeve has an external edge and the sleeve adjustment deviceadjusts the external edge to be coplanar to the probe surface.
 9. Theplasma processing chamber, as recited in claim 8, wherein the probeelement is a semiconductor probe element, wherein the probe surface is asemiconductor probe surface.
 10. The plasma processing chamber, asrecited in claim 9, wherein the sleeve adjustment device comprises atleast one removable spacer placed between the electrically insulatingsleeve and the semiconductor probe element.
 11. The plasma processingchamber, as recited in claim 10, wherein the plasma probe assemblyfurther comprises: a segmented cover surrounding the electricalconnector and at least part of the probe element; and at least oneO-ring surrounding the segmented cover.
 12. The plasma processingchamber, as recited in claim 11, wherein the plasma probe assemblyfurther comprises a support shaft wherein the adjustment device ismechanically connected to the support shaft and moves the support shaftduring adjustment.
 13. The plasma processing chamber, as recited inclaim 12, wherein the probe element comprises: a first end with theprobe surface; a second end spaced apart from the first end; and a neckportion extending between the first end and the second end, wherein theneck portion has a cross-section that is smaller than a cross-section ofthe first end and a cross-section of the second end.
 14. The plasmaprocessing chamber, as recited in claim 13, wherein the insulatingsleeve further comprises a lip, which forms an aperture through whichthe second end and the neck of the probe element are able to pass, butthrough which the first end of the probe element is not able to pass andwherein the at least one removable spacer is placed between the lip anda side of the first end of the probe element opposite from the probesurface.
 15. The plasma processing chamber, as recited in claim 14,wherein the segmented cover, comprises: a first lip that engages withthe second end of the probe element; and a second lip that engages withthe electrical connector, wherein the first lip and second lip force thesecond end of the probe element against the electrical connector. 16.The plasma processing chamber, as recited in claim 15, wherein thesecond lip has a surface with an oblique connection with the electricalconductor to force the second end of the probe element against theelectrical connector.
 17. The plasma processing chamber, as recited inclaim 15, wherein the first lip has a surface with an oblique connectionwith the electrical conductor to force the second end of the probeelement against the electrical connector.
 18. A plasma processingchamber, comprising: a chamber wall forming a plasma processing chamberenclosure; a substrate support for supporting a wafer within the plasmaprocessing chamber enclosure; at least one electrode for providing powerto the plasma processing chamber enclosure for sustaining a plasma; agas inlet for providing gas into the plasma processing chamberenclosure; a gas outlet for exhausting gas from the plasma processingchamber enclosure; and a plasma probe assembly for measuring electricalcharacteristics of the plasma, comprising: a semiconductor probe elementwith a semiconductor probe surface at a first end of the semiconductorprobe element; an electrical connector electrically connected to asecond end of the semiconductor probe element; an electricallyinsulating sleeve surrounding at least part of the probe element; anadjustment device connected to the semiconductor probe element to adjustthe semiconductor probe element so that the probe surface is coplanarwith an interior surface of the chamber wall; a sleeve adjustment devicefor adjusting the electrical insulating sleeve, wherein the electricallyinsulating sleeve has an external edge and the sleeve adjustment deviceadjusts the external edge to be coplanar to the probe surface; andsensing electronics electrically connected to the electrical connector,wherein the sensing electronics comprises an ammeter.
 19. The plasmaprocessing chamber, as recited in claim 18, wherein the probe surface issilicon.
 20. The plasma processing chamber, as recited in claim 19,wherein the electrically insulating sleeve is quartz.